fix: resolve 10 code review issues

High priority:
- Fix concurrent race condition for view_count/like_count (atomic update)
- Add route request ID tracking to prevent race conditions
- Filter get_joke by status=approved (no pending content leak)
- Add error feedback for like button

Performance:
- Optimize random joke query (avoid full table sort)
- Limit page_size max to 100 (DoS prevention)

Medium:
- Add localStorage quota error handling
- Handle empty AI response gracefully
- Fix generate content title extraction

Low:
- Add rejected_jokes to stats API
- Update dashboard to show rejected count

api/app/routers/feedback.py

@@ -0,0 +1,18 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+
+from app.database import get_db
+from app.models.feedback import Feedback
+from app.schemas.feedback import FeedbackCreate, FeedbackResponse
+
+router = APIRouter(tags=["反馈建议"])
+
+
+@router.post("/feedback", response_model=FeedbackResponse)
+def create_feedback(feedback: FeedbackCreate, db: Session = Depends(get_db)):
+    """公开：提交反馈建议"""
+    db_feedback = Feedback(**feedback.model_dump())
+    db.add(db_feedback)
+    db.commit()
+    db.refresh(db_feedback)
+    return db_feedback